1. Field of the Invention
The invention relates to the field for measuring power cables, and more particularly to a device for measuring electrical treeing in XLPE medium voltage cables.
2. Description of the Related Art
Crosslinked polyethylene (XLPE) medium voltage power cables are widely used because of convenient maintenance. However, electrical treeing in the cable insulation is always a main factor that affects the safety and stability of the cables.
Electrical treeing resistant XLPE (TR-XLPE) medium voltage power cable is a new kind of power cable that is able to prolong the service life of the XLPE cables. The production cost of the TR-XLPE medium voltage power cable is approximately 10%-20% higher than that of the common XLPE medium voltage power cable. However, these two kinds of cables have no difference in appearance, and thus, an electrical treeing experiment is required for measuring the electrical treeing resistance.
A typical method for measuring electrical treeing resistance of XLPE medium voltage power cables includes: using heat treated cables as test samples, placing each cable inside a polyethylene tube or a polyvinyl chloride tube having an inner diameter of 75 mm, and applying a test voltage to facilitate the electrical treeing. During the electrical treeing test, water is injected into the interspace of conductors of the test samples and the tubes. The test samples are required to be heated by inductive current for load cycles, and then examine and count the electrical treeing after the test.
The method has the following disadvantages:
1) the method can only take cable core of finished power cable as test sample; the test device has a large volume and the operation for the test is complicate and cumbersome; and
2) the test period for electrical treeing is long; performing the electrical treeing test on the test samples is time consuming, so that the method cannot fast evaluate whether the cable materials have the property of electrical treeing resistance.